In network architectures, different service models for roaming subscribers may be provided. When a user is roaming, a control means or control function such as Serving-CSCF “Call State Control Function”, to which a subscriber is registered and where the connection control such as the call state control is handled, may still be located in the home network. In such a home service model, it is important to pass different kinds of information from the visited network to the home network for proper connection control.
Solutions proposed for emergency calls are not applicable to general cases where service should be chargeable and thus the bill sender, i.e. the home network operator, should also be able to prevent its use.
In third generation mobile networks telephony and multimedia services can be provided by IP Multimedia Subsystem (IMS). In 3GPP (3GPP=3rd Generation Partnership Project) standardization it has been decided that services are controlled by subscriber's home network even when the subscriber is roaming in some visited network. It is however required that the visited network allows access to services of a local nature to visiting subscribers (inbound roamers) as well. This should be achieved with minimal changes to the current IMS architecture.
WO 02/13567 (corresponding to PCT/EP00/07779, the disclosure contents of which are herewith fully incorporated into the present application) discloses a communication method and system wherein during call setup or registration of a User Equipment (UE) having roamed to a visitor network, a Proxy-CSCF (Call State Control Function) in the visited network assists the Serving CSCF in the home network by providing information about the local destination. This information is provided in a SIP (Session Initiation Protocol) request from the User Equipment. By providing information about the local destination, the home network is able to correctly handle (route, charge, ban, etc) the calls/sessions originated from the visited network.)